Within the data storage industry, data storage devices typically include a head for reading and/or writing data onto a storage medium. Storage device examples include magnetic and optical devices. The storage medium may be in the form of a disk which may be flexible or rigid depending on the disk drive. An actuator mechanism is used for positioning the read/write head at specific locations or tracks in accordance with the disk drive usage. Linear and rotary actuators are known based on the manner of movement of the head. Head suspensions are provided between the actuator and the head and support a slider in proper orientation relative to the disk surface.
In a rigid disk drive incorporating one or more disks, head suspensions are provided for supporting a head slider to "fly" over the surface of the rigid disk when it is spinning. Specifically, the head is usually located on an aerodynamically designed slider which flies on an air bearing generated by the spinning disk. In order to establish the fly height, the head suspension is also provided with a spring force that counteracts the aerodynamic lift force generated by the air bearing.
A suspension assembly of the type used in a rigid disk drive comprises the head slider and the head suspension, the head suspension comprising a load beam and a flexure. Load beams normally have an actuator mounting region, a rigid region and a spring region between the actuator mounting region and the rigid region for providing the aforementioned spring force. A bend in the form of a radius within the spring region can be used to provide the spring force. The flexure is provided at the distal end of the load beam from the actuator mounting region and provides a slider mounting pad to which the head slider is mounted and which is designed to permit pitch and roll movements of the head slider to follow disk surface fluctuations. Many types of flexures have been developed including flexures that are integrated into the design of the load beam and those formed as a separate element and fixed to the rigid region of the load beam.
In order to permit pitch and roll movements of the head slider, flexures typically include a cantilever portion having a free end which is resiliently movable relative to the remainder of the flexure. Depending on the design, more than one movable end may be provided. In the case of integrated flexures or gimbals, a slider bond pad is usually supported by one or more sets of bridges that define pitch and roll axes and which extend from the rigid region of the load beam. The bridges are designed to be sufficiently resilient so that they can flex to permit the pitch and roll movements of the head slider during usage.
Developments are being made for increasing the storage capacity of hard drives and in the reduction of the size of the hard drives to facilitate smaller and more powerful computers. In a rigid disk drive, the rigid disks are typically provided in a stack on a spindle. Likewise, the head sliders are supported by a stack of head suspensions, each of which is connected with the actuator assembly for moving the stack of head suspension and head slider assemblies over the respective surfaces of the rigid disks. The actuator may be linear or rotary as defined by the movement of the head sliders. By decreasing the spacing between the disks within such a stack, greater storage capacities can be achieved. Moreover, even with smaller disks and smaller size restrictions, with increased storage densities of the disks, much greater capacities can be achieved in even smaller spaces. Greater storage density of the disks require that the head sliders fly closer to the disk surface during use.
The spacing of the rigid disks, however, and more importantly the space between the disks, is limited by the ability to insert and position the suspension assembly or assemblies within the space. Thus, to enable closer disk spacings, it may be desirable to reduce the thickness of the suspension assemblies including the thickness of the head suspension and the thickness of the head slider. It is important, however, when attempting to reduce thickness to maintain performance characteristics of the head suspension. Simply making the head suspensions, for example, from a thinner material can have a deleterious effect on performance. Head suspensions are designed to have stiffness characteristics in its bending modes, torsional modes, and lateral bending modes. Performance must be particularly controlled at the resonance frequencies of the specific modes. Thus, to use thinner materials, other design features may need to be incorporated such as using higher side rails or other stiffening features to enhance stiffness to control any of the various modes.
Another component in the construction of its suspensions is the interconnect assembly for relaying signals to and from the head along the head suspension assembly. At the actuator mounting end of the head suspension, the interconnect assembly connects with the amplifying and control electronic circuits of a disk drive. Traditional interconnect assemblies include multiple conductors, usually two or four, comprising copper wires encapsulated in plastic sheathing.
Interconnect assembly conductors can have a large effect on the head suspension assembly performance. Conductor stiffness alone can dramatically affect the rigidity of the spring regions and flight performance. The connection of the conductors to the head slider can place unwanted torques or biases on the head slider. Moreover, the positioning and connecting of wires is a labor intensive endeavor. Electrical flex circuits have also been developed, but basically have the same drawbacks. Additionally, the interconnect assembly itself adds to the thickness or side profile of the head suspension which must be taken into account for disk spacing.
A more recent development is the introduction of head suspensions having leads or conductors integrated or patterned directly onto the surface of the load beam and/or flexure. Examples include the head suspension and interconnect assemblies described in U.S. Pat. Nos. 5,391,842 and 5,491,597 and U.S. patent application Ser. Nos. 08/249,117 and 08/478,396, each of which is owned by the assignee of the subject application. The basic concept is that the integrated lead is patterned onto the load beam with a layer of dielectric material for insulation between the conductive material and the load beam. The main advantage is that the conductors can be precisely located and may be made in a process integral with the load beam. Thus, the characteristics of the load beam including its interconnect assembly are much more highly predictable. Of the above examples, U.S. patent application Ser. Nos. 08/249,117 and 08/478,396 also disclose the use of the conductive material of the integrated leads as an integral part of the flexure or gimbal assembly. That is, the conductive material provides a mechanical interconnect, such as between the load beam and a slider bond pad, as well as the electrical interconnect to the head slider.
Another advantage of integrated lead conductors is that they can be made relatively thin on the load beam surface so as to require minimum spacing between disks of a disk drive. However, even with such an interconnect assembly having a conductor acting as both the mechanical and electrical connection to the slider bond pad, it is necessary that the flexure or gimbal provide the necessary clearances to allow adequate pitch and roll movement of the head slider when mounted to the slider bond pad. Typically, this means forming offsets within either a portion of the flexure construction, possibly within the conductive material, so as to offset the head slider sufficiently from the load beam to permit adequate pitch and roll.